The present invention relates to a stripping column installation especially for separating starting materials with a high boiling point difference. More particularly, it relates to such a stripping column installation which has a stripping column with a column sump (a lower column port for draining), and a circulating boiler connected with the column sump and provided with pipe bundles through which a sump product flows from the stripping column.
Stripping columns of the above mentioned general type are known in the art. In a stripping column in which heating of the distillative starting material to be separated into its components is performed, the sump product or a portion of it is withdrawn from the stripping column, heated or evaporated in the circulating boiler in indirect heat exchange with a heating medium and then again supplied into the stripping column. The circulating boiler is normally provided with a vertically or horizontally arranged pipe bundle. The sump product flows through the pipe bundle and the pipe bundle is heated from outside by the heat exchange medium. An example of such a column is disclosed for example in "Ullmanns Encyklopadie der technischen Chemie," 4th edition, Vol. 2, page 506, FIG. 34. Such stripping column poses certain problems for preparation of starting products with a high boiling point difference, or in other words starting products in which the boiling points of the highest boiling component and the lowest boiling component are very different from one another. In these cases, only a convective heat transfer occurs in the pipe bundle of the circulating boiler over a greater part of its pipe length. An evaporation is not possible in this region since here the vapor pressure of the low boiling components of the starting products lies below the total pressure of the liquid column. Since moreover in many cases for operational reasons only a one-time passage of the sump product withdrawn from the stripping column is performed through the circulating boiler, only moderate and in many cases very low heat transfer values are obtained in the region of the convective heat transfer. This problem can be taken care of by an increase of the heat exchange surfaces. This leads however to an increase of the total circulating boiler which is naturally expensive. In addition, in many cases such an increase contradicts operational conditions.